a-Fucosidase

Principle Of Method:
Hydrolysis of the synthetic substrate 4-methylumbelliferyl-a-L-fucopyranoside at acid pH is followed by measuring the fluorescence of the liberated 4-methylumbelliferone after stopping the reaction with alkaline buffer.

Uses And Limitations Of The Method:Deficiency of lysosomal a-fucosidase is the primary defect in fucosidosis, leading to storage of oligosaccharides and glycopeptides with an a-fucose residue at the non-reducing terminals. The assay is run routinely as part of the laboratory’s lysosomal enzyme screening procedure. a-fucosidase is elevated in plasma from patients with I-cell disease and pseudo-Hurler polydystrophy. Prenatal diagnosis of fucosidosis is possible following CVS or amniocentesis, but heterozygote detection is not reliable. Although fucosidosis patients exhibit an abnormal oligosacchariduria, the pattern is not very distinctive and the enzyme assay must be performed to confirm or exclude the diagnosis.